It is known to provide overhead rail systems upon which a vehicle can be mounted for the transport of goods, people, etc. Generally such an assembly comprises a plurality of uprights, i.e. support masts or pylons, spanned by the relatively rigid rail upon which the vehicle is adapted to ride.
In another system, the rails are suspended from a support cable which can be slung between the support masts where, for example, suspenders hang vertically from the suspension cable to engage the rail. Such systems have been made and marketed by Eberfeld-Barmen, GERMANY, and can span distances of several hundred meters between support masts or posts as opposed to distances of only 10 to 15 meters where rigid rail structures are employed.
However, while cable-supported rails can span far greater distances than rigid rails, the vehicle speed in cable-suspended rails must be low. This is because of the downward bow of the rail between the supports and the crowning of the wire upwardly in the region of the supports.
The sag of the cable between the support masts or pylons has previously been the subject of investigation and it has been proposed (see German open application-Offenlegungsschrift--DT-0S 2 149 871) to provide a negative sag, i.e. an upward bow, which will compensate for the load applied by the vehicle so that the vehicle travels only over a straight line stretch into which the rail is deflected against the contrary loading necessary to bring about the negative sag. The travel path is thus approximately straight. In spite of the fact that the sag during travel appears to be eliminated by this technique, experiments with it have shown that it does not have the desired effect, namely, does not allow a substantial increase in speed.
In that prior-art system the "track" is a wire or cable from which the vehicle is suspended. In German open application--Offenlegungsschrift-DT-0S 1 905 686, the track-forming cable is replaced by a rail which is suspended in the manner described previously so that stretches of the rail between the masts or pylons are bowed upwardly. All of these systems have the aforementioned negative sag whether the track is in the form of a cable or rail. Also all have the disadvantage that, in an unloaded state of the track, at the masts or posts, crimps are formed in the track in the regions in which it is suddenly deflected upwardly by the negative sag arrangement. This is because at the pylons or masts, a downward reaction force must be applied to the track to keep the same from moving upwardly to follow the upward prestress inducing the negative sag.
Even when the vehicle is traveling along the track so that its load balances the upward force producing the upward sag, the crimping of the track at the support or pylon remains. In this region the vehicle must make a transition between the loaded and unloaded stretches of the track. The crimped parts of the track reduce the maximum speed which can be developed therealong, give rise to excessive wear and, in general, have been found to be unsatisfactory.